Golf courses undulate. That is, even relatively easy and relatively flat golf courses have ups and downs, peaks and valleys, sand dunes, raised tee off areas, and raised greens. Further, even if a fairway happens to be like a pancake, the fairway may dogleg to the left or dogleg to the right to provide an undulation from another perspective.
Each and every golf course is a unique piece of property. The unique features of a golf course are many. A few of these unique features are natural features found prior to development such as lakes, ponds and streams. Other unique features are manmade: the layout, the total yardage, the width of the fairways, and the size of the greens.
Faces, like golf courses, are unique and undulating. The application to a face of a face mask having a single seal is like a game of golf with no Mulligans, but infinitely more serious.